Understanding the EPA's upcoming regulation of ATVs and the fate of 2-cycle engines

You may have heard the rumor that the Environmental
Protection Agency is forcing ATV manufacturers to install exhaust
catalysts on your favorite sport quad. Or that in 2006 two-stroke
ATV's will be out-lawed. Well, it's not exactly true, but not too
far off. Back in 1990 the Clean Air Act was passed which
essentially called for the clamping down of the exhaust emissions
from cars and light trucks. Since that time, the stuff emitted from
the tailpipes of cars and trucks has been cleaned up so well, that
in some cases the air coming OUT of the tailpipe is actually
cleaner than what's going in the intake. The ultimate effect has
been steadily decreasing air pollution levels even though the
number of vehicles on the road has increased by over double since
the time study was begun.

Air pollution over the last 35
years has steadily improved since the Clean Air Act was instated,
especially surprising considering the dramatic increase in how much
we Americans drive.

Not ones to be satisfied with good enough, the EPA
has shifted their attention to motorcycles - on-road bikes, as well
as off-highway motorcycles (OHMCs), snowmobiles, and ATVs.
Nationwide, these vehicles account for nearly 10% of national
hydrocarbon emissions (HC), and almost 5% of carbon monoxide (CO).
Put into perspective, a typical two-stroke ATV produces as much
pollutant as a dozen modern cars.

Although these machines represent a considerably
small percentage of emission producing vehicles, they do
nonetheless produce many nasties that left unchecked long enough,
can have a very negative impact on the environment and our sport.
Take the case of Yellowstone National Park which although for many
years enjoyed a reputation of being a fantastically beautiful place
to go snowmobiling, had to completely shutdown motorized winter
recreation due to the seemingly omni-present blue cloud of
two-stroke smoke that would blanket the area in the
wintertime.

But what are these "pollutants" and why do we care?
Having spent many years sniffing the exhaust of motorcycles, many
of us can probably, with little sarcasm, admit to actually enjoying
the sweet smell of burnt racing fuel. The darker side to fuel
combustion is that it's not perfect. If it was perfect, the complex
hydrocarbon compounds of the fuel (Hydrogen and Carbon molecules)
would react with air (Oxygen and Nitrogen molecules) and produce
very benign molecules of CO2 (carbon dioxide), H20 (water), and N2
(nitrogen). Theoretically that's how it works. But unfortunately,
it doesn't work out so nicely in the intense heat of an engine, and
we get CO (carbon monoxide), unburnt hydrocarbons (HCs), some
water, and various oxides of nitrogen (NOx) as the products of
combustion. All but the water are very bad for you.

As for those bad actors, we all know that CO is a
colorless, odorless gas that can kill you if you spend too much
time behind closed doors listening to the drone of your beloved
bike. But with over a million pounds of CO per year pouring out of
ATVs alone, the cumulative effect of all motor vehicles is
significant and detrimental on those with weak cardio-vascular
systems.

The infamous LA smog pictured above is primarily
ground-level ozone (O3), which is formed by chemical reactions of
volatile organic compounds (primarily HC) and NOx in the presence
of heat and sunlight. Not only is the effect unsightly, but can
cause real problems with the respiratory system (lung damage). If
left uncontrolled, the EPA expects that off-road vehicles will
constitute a fourth of the total HC emissions from mobile sources
by 2020.

Engine category

ATV emission rates (grams /
mile)

HC

CO

NOx

PM

current
2-stroke

53.9

54.1

0.2

2.1

current
4-stroke

2.4

48.5

0.4

0.1

EPA
std.

1.6

42.9

0.3

0.1

To head this off at the pass, the EPA has instituted
regulation of nonroad engines nationwide starting in 2006. At that
time, half of a manufacturer's new motorcycle models must meet the
regulation. By 2007, every new machine (with the exception of
"competition-only" machines) must meet the standard, or it cannot
be sold or operated in the United States. They have not
specifically declared how the OEMs are to meet the requirement,
only that they must. And herein lies the fate the ubiquitous
2-stroke.

Although the two cycle engine design can pack a lot
of power in a small package, it does so with the compromise in
efficiency. The beauty of the design is that it can accomplish all
four required internal engine events (suck-squish-bang-blow) in a
single revolution of the crankshaft. That means that it has twice
as many power strokes per rev than the arguably more refined
4-stroke. That's where the superior power comes from, not
from anything magical or inherently better about the engine design.
In fact, it's quite crude in comparison to the 4-stroke which has
valves to control the gas exchange process in a much more
regimented manner. And there's the rub - as powerful as the
2-stroke is, it accomplishes it at the expense of wasted fuel that
escapes the combustion process. Not only do the engines expel
comparatively more HC (unburnt gasoline) due to imperfect
scavenging, but there's also additional HCs in the exhaust in the
form of burnt and unburnt 2-cycle oil. Even with the most advanced
electronics and engine technologies, it will be nearly impossible
for a 2-cycle powered ATV to become certified.

So what will this mean? The industry has been seeing
the evolution to 4-stroke powerplants now for several years which
is certain to continue. The good news is that the motorcycle
manufacturers are building ultra high-tech 4-strokes that are
rivaling the power of their ill-fated caustic cousins. Down the
road, as in 2009 when an even tighter regulation is put in place,
it wouldn't be unrealistic to start seeing exhaust catalysts and
even fuel injection of your favorite quad. For the Japanese market,
Honda plans by 2007 to have every single one of their motorcycles
fuel injected - from their 180 mph superbikes, down to their 50cc
scooters. The upshot is that when the emission standards for
recreational vehicles are fully implemented by all the OEMs, the
EPA expects to cut in half the HC, NOx, and CO emissions from these
engines by 2020. For those that ride, or don't ride, that'll
mean fresher air, less trips to the doctor, and no more blood-shot
eyes at supercross races.